Adhesive film constructions with detectable transparent release liners

ABSTRACT

The present invention provides adhesive film constructions that include a detectable transparent release liner. The release liner includes a transparent polymeric core and one or more detection stripes. The detection stripes are parallel to the longitudinal length of the construction. By providing a release liner that is transparent over a majority of its major surfaces (except for the detection stripes), the problem of edge detection when using transparent liners and/or transparent adhesive film constructions can be addressed without significantly degrading the ability to see through a majority of the film and liner composite.

Field of the Invention

[0001] The present invention relates to the field of adhesive film constructions including detectable transparent release liners and methods of manufacturing the same.

BACKGROUND

[0002] Adhesive-coated films are often supplied with release liners to protect the adhesive from contamination before application of the film to a desired surface. The adhesives are often pressure sensitive adhesives, making them easily contaminated with dirt and other debris. In addition, the release liner makes the adhesive-coated films more easily handled and transported by preventing the adhesive-coated film from adhering to itself or other surfaces.

[0003] Many release liners are based on paper substrates that are coated with some material or materials that provides the desired release characteristics for the adhesive to be used in connection with the release liner. Although paper is relatively inexpensive as a release liner substrate, it does offer a number of disadvantages.

[0004] For example, paper can tend to absorb moisture, thereby degrading its mechanical properties. Water absorbed by the paper release liner may also be detrimental to the adhesive that is intended to be protected by the liner. In addition, a paper liner that has absorbed moisture may tend to curl or otherwise deform from an otherwise flat shape, thereby curling the adhesive-coated film attached to the release liner.

[0005] Other disadvantages of paper release liners is that the liner is typically opaque, i.e., an image beneath the film/adhesive/liner composite is not readily viewed. As a result, alignment of images on different films provided on different liners can be difficult or impossible when using paper release liners. Alignment may, however, be critical when multi-color layups are needed, with the different colors being provided on different film provided on different liners.

[0006] Transparent polymeric release liners have been used to address some of these issues. The polymeric liners typically absorb little or no moisture, thereby retaining their mechanical properties (e.g., strength, shape, lay-flat performance, etc.). The polymeric liners can also be provided as transparent films to assist in the production of multi-color layups. When used as part of the composite of film/adhesive/release liner, a transparent release liner allows viewing of a second image that is located beneath the film/adhesive/release liner composite.

[0007] One potential disadvantage of such transparent release liners is that they may not be readily sensed or detected by many of the web guide systems used with the liners. The adhesive coated films may be processed in sheet form or as continuous length webs. In either case, the apparatus used to process the film constructions often rely on edge detection for proper steering of the films through the apparatus.

[0008] If the film and/or liner are transparent, they may not be readily detect by some sensors, e.g., ultraviolet-based sensors (such as those detecting light at wavelengths of about 472 nanometers (nm)). As used herein, “transparent” means films and other substrates or materials that do not absorb or scatter light in sufficient amounts to permit accurate detection by sensors operating in the ultraviolet range of the electromagnetic spectrum. As a result, the films and/or liners may track off-center, thereby adversely affecting processing.

[0009] Problems may also be experienced when using transparent release liners on perforated films, e.g., one-way vision films such as those marketed by Minnesota Mining and Manufacturing Company, St. Paul, Minn. (Series 8171 and 8671 Graphic Films). Some sensors may detect the perforations and cease processing. As a result, some film processing systems cannot be used with perforated adhesive films on transparent release liners.

SUMMARY OF THE INVENTION

[0010] The present invention provides adhesive film constructions that include a detectable transparent release liner. The release liner includes a transparent polymeric core and one or more detection stripes As noted above, the term “transparent” means that the recited component does not absorb or scatter light in sufficient amounts to permit accurate detection by sensors operating in the ultraviolet range of the electromagnetic spectrum. The detection stripes are not “transparent,” i.e., they absorb or scatter light in sufficient amounts to permit accurate detection by sensors operating in the ultraviolet range of the electromagnetic spectrum. The detection stripes are parallel to the longitudinal length of the construction. By providing a release liner that is transparent over a majority of its major surfaces (except for the detection stripes), the problem of edge detection when using transparent liners and/or transparent adhesive film constructions can be addressed without significantly degrading the ability to see through a majority of the film and liner composite.

[0011] The detection stripes may be located proximate one or both edges of the release liner. In addition, it may be desirable to include one or more detection stripes between the edges of the film, particularly if the film is to be slit to narrower widths during processing, thereby forming new edges that may require detection. Those new edges are preferably formed within one of the detection stripes such that they can be readily detected during processing.

[0012] By locating the detection stripes on the release liner, the other components of the film construction can remain unchanged. For example, the entire width of the adhesive-coated film may be used without requiring alteration to detect its edges. Furthermore, the transparent release liner with detection stripes can be used on transparent adhesive-coated films or on adhesive-coated films that are not transparent, thereby potentially reducing the need to stock additional liners based on their detection properties.

[0013] The films used in connection with the present invention are typically described as having a continuous length. As used herein, a “continuous length film” is a film having two opposing sides extending along a length, wherein the distance between the two opposing sides defines the width of the film. The length of a “continuous length film” is substantially greater than its width, e.g., about 2 or more times greater than the width, in other instances about 20 or more times greater than the width of the film.

[0014] In one aspect, the present invention provides an adhesive film construction including a continuous length film with opposing edges extending along a length of the film; adhesive located on a first major surface of the film; a transparent release liner attached to the film over the adhesive; and at least one detection stripe on the transparent release liner, the at least one detection stripe extending along substantially all of the length of the film, wherein the at least one detection stripe is parallel to the opposing edges of the film, whereby removal of the release liner from the adhesive removes the at least one detection stripe from the adhesive film construction.

[0015] In another aspect, the present invention provides adhesive film construction including a continuous length film with opposing edges extending parallel to each other along a length of the film; adhesive located on a first major surface of the film, wherein at least a portion of the film and the adhesive are transparent; a transparent release liner attached to the film over the adhesive; and a plurality of detection stripes on the transparent release liner, the plurality detection stripes including a coating on the transparent release liner, wherein each detection stripe of the plurality of detection stripes extends along substantially all of the length of the film, wherein each detection stripe of the plurality of detection stripes is parallel to the opposing edges of the film, wherein the plurality of detection stripes occupy about 20% or less of a major surface of the release liner, and wherein the plurality of detection stripes occupy about 1% or more of the major surface of the release liner; whereby removal of the release liner from the adhesive removes the plurality of detection stripes from the adhesive film construction.

[0016] In another aspect, the present invention provides a method of processing an adhesive film construction of the present invention, the method including threading the adhesive film construction into a film processing sensor, wherein the processing system includes a film sensor; detecting at least one of the detection stripes with the film sensor; and manipulating the adhesive film construction based on the detecting.

[0017] These and other features and advantages of the present invention may be described below in connection with various illustrative embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a cross-sectional view of one adhesive film construction according to the present invention.

[0019]FIG. 2 is a cross-sectional view of a release liner including a core and coatings thereon.

[0020]FIG. 3 is a perspective view of a release liner for use in connection with the present invention.

[0021]FIG. 4 is a perspective view of another release liner for use in connection with the present invention.

[0022]FIG. 5 is a schematic block diagram of one film processing system for use with adhesive film constructions of the present invention.

DETAILED DESCRIPTION OF ILLUSTRSTIVE EMBODIMENTS OF THE INVENTION

[0023]FIG. 1 is a cross-sectional view of one adhesive film construction 10 according to the present invention. The construction 10 includes a film 20, adhesive 30 located on a major surface of the film 20, and a release liner 40 attached to the film 20 over the adhesive 30.

[0024] The film 20 may include one or more images if so desired. Alternatively, the film 20 may merely exhibit a desired color or some other effect. The film 20 may be substantially transparent, with an image 26 formed thereon by any suitable technique, e.g., printing, etc. Although that image 26 may itself not be transparent and may extend to the edges 22 and 24 of the film 20, it may do so in a discontinuous manner, i.e., the image may not be continuous along the edges 22 and/or 24 of the film 20. As a result, the image 26 cannot be relied on for accurate edge detection along the length of the film 20.

[0025] In other constructions, the film 20 may be perforated, such that it includes voids formed therethrough. Examples of such perforated films include, e.g., one-way vision films such as those marketed by Minnesota Mining and Manufacturing Company, St. Paul, Minn. (Series 8171 and 8671 Graphic Films).

[0026] The construction 10 also includes an adhesive 30 that is preferably provided in the form of a substantially continuous layer on one of the major surfaces of the film 20. If an image is present on the film 20, the adhesive 30 is typically located on the major surface of the film 20 that is opposite the major surface carrying the image.

[0027] Any suitable adhesive may be used, e.g., pressure-sensitive adhesives, curable adhesives, heat-activated adhesives, etc. It may be preferred, however, that the adhesive 30 be a pressure-sensitive adhesive that is compatible with the film 20, release liner 40 and any surface to which the film 20 is to be adhered. The film 20 and adhesive 30 may be supplied together.

[0028] A release liner 40 is attached to the film 20 over the adhesive 30 to protect the adhesive 30 from contamination before use. The release liner 40 may also provide additional structural integrity to the film 20 during processing. Furthermore, the release liner 40 may be used as a vehicle for information regarding the adhesive-coated film 20. For example, the release liner 40 may include information regarding the film 20 (e.g., its composition, intended use, application instructions, etc.). In addition, the release liner 40 may include indicia such as logos, etc. indicative of the source of the film 20.

[0029] Referring to FIG. 2, a cross-sectional diagram of the release liner 40 is depicted, illustrating the core 41 of the liner 40. The core 41 is preferably constructed of a transparent polymeric material or materials. One or both of the major surfaces of the core 41 may be coated with various layers 43 and 45 to, e.g., control adhesive release characteristics, improve the ability to print on the release liner 40, etc. Regardless of the coatings used, it is preferred that the completed release liner 40, including the core 41 and any layers applied thereto, is transparent as defined herein.

[0030]FIG. 3 depicts the release liner 40 with detection stripes 50 a and 50 b (referred to collectively as detection stripes 50). The release liner 40 is, itself, transparent as discussed above. The liner 40 does, however, include detection stripes 50 to assist in edge detection of the release liner 40 alone and edge detection of the film 20 when the film 20 and release liner 40 are attached to each other such that their respective edges are aligned.

[0031] The release liner 40 includes at least one detection stripe 50 located proximate at least one edge 42, preferably both edges 42, of the liner 40. The detection stripes 50 are not transparent. As a result, the detection stripes 50 can be detected by sensors operating in the ultraviolet range of the electromagnetic spectrum. By detecting the detection stripes 50, the release liner 40 (and any other components, e.g., film 20, attached to the release liner 40) may be steered through a processing apparatus.

[0032] The detection stripes 50 are continuous over the length of the adhesive film construction on which the release liner 40 is to be used. That length is typically coextensive with the length of the release liner 40 and extends in the directions of arrow 46 as depicted in FIG. 3. The detection stripes 50 are preferably located along the edges 42 of the release liner 40, although in some instances they may be set in from the edges 42 of the release liner 40 (see FIG. 4 and related description below).

[0033] The detection stripes 50 preferably occupy a relatively small portion of the major surfaces of the release liner 40. By limiting the amount of surface area covered by the detection stripes 50, more of the underlying adhesive film 20 may be viewed. It may, for example, be preferred that the detection stripes 50 occupy about 30% or less of the surface area of the release liner 40, more preferably about 20% or less of the surface area of the release liner 40. At the other end of the spectrum, it may be preferred that the detection stripes 50 occupy at least about 1% of the surface area of the release liner 40. Alternatively, it may be preferred that the detection stripes 50 have a width (as measured transverse to the length of the adhesive film construction) of at least about 1 cm, more preferably at least about 2 cm.

[0034] Referring to FIG. 4, a transparent release liner 140 is depicted and includes four detection stripes 150 a, 150b, 150 c and 150 d (referred to collectively as detection stripes 150). All of the detection stripes 150 are set inward from the edges of the liner 140.The use of more than two detection stripes 150 may allow for slitting of the release liner 140 into multiple widths, with the reduced width release liner still retaining a detection stripe 150.

[0035] The detection stripes used on release liners of the invention may take a variety of forms. They may be provided as coatings (dyes, inks, pigmented coatings, etc.) on either major surface of the release liner, they may be provided in the form of a tape attached to the release liner, etc. If the detection stripes are provided in the form of a coating, it may be preferred that another protective coating be applied over the detection stripes to protect them from damage, etc.

[0036] As discussed above, the detection stripes, regardless of their physical form, are not transparent, i.e., they absorb or scatter light in sufficient amounts to permit accurate detection by sensors operating in the ultraviolet range of the electromagnetic spectrum. The non-transparent properties of the detection stripes may, in some instances, be quantified based on optical transmission density. For example, it may be preferred that the portions of the release liner including the detection stripe exhibit a nominal optical density of about 0.7 or higher, more preferably about 0.8 or higher (when measured using a MacBeth Transmission Densitometer (GretagMacBeth LLC, New Windsor, N.Y.) with a blue light filter, thereby generating light with a wavelength of about 470 nanometers)

[0037]FIG. 5 is a schematic diagram of one film processing system 60 according to the present invention. The processing system 60 includes a film sensor 62 that, in preferred embodiments, emits ultraviolet electromagnetic energy to detect edges on adhesive film constructions. The adhesive film construction can then be manipulated based on detection of the film edges.

[0038] The manipulation can include feeding the adhesive film construction through the film processing system 60 (where, e.g., the film sensor 62 provides an indication that an adhesive film construction is present for processing by the film processing system 60). Manipulating may alternatively involve steering the adhesive film construction through the film processing system 60 based on the feedback from the film sensor 62.

[0039] When used with adhesive film constructions that include transparent release liners with at least one detection stripe, the detection stripe can be detected by the film sensor 62 because the detection stripe will block or scatter at least a portion of the energy emitted by the film sensor 62 to enable detection where it could not otherwise be obtained due to the transparent nature of the release liner.

[0040] Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope of this invention. Accordingly, it is to be understood that this invention is not to be limited to the illustrative embodiments set forth herein, but is to be controlled by the limitations set forth in the following claims and any equivalents thereof. 

What is claimed is:
 1. An adhesive film construction comprising: a continuous length film that comprises opposing edges extending along a length of the film; adhesive located on a first major surface of the film; a transparent release liner attached to the film over the adhesive; and at least one detection stripe on the transparent release liner, the at least one detection stripe extending along substantially all of the length of the film, wherein the at least one detection stripe is parallel to the opposing edges of the film, whereby removal of the release liner from the adhesive removes the at least one detection stripe from the adhesive film construction.
 2. A construction according to claim 1, wherein the at least one detection stripe comprises a coating on the transparent release liner.
 3. A construction according to claim 1, wherein the at least one detection stripe comprises a tape attached to the release liner.
 4. A construction according to claim 1, further comprising two or more of the at least one detection stripes.
 5. A construction according to claim 1, further comprising three or more of the at least one detection stripes.
 6. A construction according to claim 1, wherein the film comprises a transparent film.
 7. A construction according to claim 1, wherein the film comprises a transparent film, and further wherein the film comprises an image located thereon.
 8. A construction according to claim 1, wherein the film comprises a perforated film.
 9. A construction according to claim 1, wherein the film comprises a perforated one-way vision film.
 10. A construction according to claim 1, wherein the at least one detection stripe occupies about 30% or less of a major surface of the release liner.
 11. A construction according to claim 1, wherein the at least one detection stripe occupies about 1% or more of the major surface of the release liner.
 12. An adhesive film construction comprising: a continuous length film that comprises opposing edges extending parallel to each other along a length of the film; adhesive located on a first major surface of the film, wherein at least a portion of the film and the adhesive are transparent; a transparent release liner attached to the film over the adhesive; and a plurality of detection stripes on the transparent release liner, the plurality detection stripes comprising a coating on the transparent release liner, wherein each detection stripe of the plurality of detection stripes extends along substantially all of the length of the film, wherein each detection stripe of the plurality of detection stripes is parallel to the opposing edges of the film, wherein the plurality of detection stripes occupy about 20% or less of a major surface of the release liner, and wherein the plurality of detection stripes occupy about 1% or more of the major surface of the release liner; whereby removal of the release liner from the adhesive removes the plurality of detection stripes from the adhesive film construction.
 13. A method of processing an adhesive film construction manufactured according to claim 1, the method comprising: threading the adhesive film construction into a film processing sensor, wherein the processing system comprises a film sensor; detecting at least one of the detection stripes with the film sensor; and manipulating the adhesive film construction based on the detecting.
 14. A method according to claim 13, wherein the film sensor emits ultraviolet electromagnetic energy, and further wherein the detecting comprises detecting at least a portion of the ultraviolet electromagnetic energy emitted by the film sensor.
 15. A method according to claim 13, wherein the manipulating comprises feeding the adhesive film composite through the film processing system.
 16. A method according to claim 13, wherein the manipulating comprises steering the adhesive film composite within the film processing system. 